Microsoft's Windows 10 will not have a fragmentation problem, analysts argued, even though its rapid development tempo and a host of update cadences will spin off so many versions that not everyone will be running the same code, or even have the same features, at any one time.

"There will undoubtedly be some fragmentation of the installed base due to timing but it shouldn't be extreme, and indeed should be better than the situation today," contended Steven Kleynhans of Gartner.

For Kleynhans and others, Windows 10 will ultimately be an improvement over the current situation, where the majority are on Windows 7, but sizable numbers remain on other editions, notably 2012's Windows 8 and 2013's follow-on, Windows 8.1, and 2001's Windows XP, each of which is significantly different.

Still, Windows 10 will not exactly be the monolithic operating system that Microsoft has portrayed: The same code running on a billion systems.

Because Microsoft will be constant tweaking, refreshing and upgrading the OS, it will be a moving target compared to past editions, which once finished were generally left alone, serviced by security patches and behind-the-scenes bug fixes, but not significantly altered.

Different models

The Redmond, Wash. company experimented with a different model with Windows 8.1, which shipped a year after its Windows 8 parent with new features and functionality, and some limited user interface (UI) and user experience (UX) modifications. That practice has been both greatly expanded and accelerated with Windows 10, which will receive updates about three times a year.

But the churn of Windows 10 changes isn't the only new practice in play: The multiple release tracks Microsoft is to offer will result in some users running Build n, while other run n-1 and still others n-2 (where n is the most current). Those tracks -- Microsoft calls them "branches" -- will offer customers a range of update and upgrade tempos, from the previews handed to Windows Insider participants to the automatic get-everything Current Branch (CB) for consumers to the Current Branch for Business (CBB), which allows for delayed deployments.

The multiple tracks will create several "forks" in Windows 10 once the operating system starts to deliver the three-times-a-year updates and upgrades. By Computerworld's count, which was based on Microsoft's description of the process earlier this year, in October 2016 there will be three builds active simultaneously: The original Build 1 released in December 2015 (still being run by those on the CBB track who have postponed the update using Windows Server Update Services, or WSUS), April 2016's Build 2 (still allowed via CBB served by Windows Update for Business, or WUB), and Build 3, issued in August 2016 (consumers on the CB track).

Any given build, say No. 1, can be in use somewhere over a 16-month stretch.

And that doesn't even count Windows Insiders, who will presumably be on some kind of preview of Build 4 as it works its way to a December 2016 release to CB. "Insider is only beta testing and not for production," noted Gary Chen of IDC, essentially discounting the preview program from the forks discussion because of its limited appeal.

According to Microsoft, some five million users are now running Insider -- a paltry number compared to the 1.5 billion running some form of Windows -- but data from metrics firm Net Applications indicates that the number is half that, about 2.6 million.

Where Insider rings fit in

Complicating matters are the "rings" that Microsoft has used in the Insider program, and will replicate in the other branches. Through the months-long Insider, Microsoft has offered testers a "slow" ring and a "fast" ring, with the latter pushing updates more frequently, the former less often but with more stable code.

Microsoft has said that the CBB branch, and by implication the CB branch as well, will have rings of their own -- perhaps the same fast and slow of Insider -- so users have some choice about when they receive updates and upgrades. In May, OS head honcho Terry Myerson said, "There will be new rings specifically for enterprises, for businesses that want to be in slower rings to make sure all the kinks are worked out in any updates before it gets applied to their system."

Adding rings to the branches, assuming two rings per, doubles the number of different versions active at any one time.

Meanwhile, large organizations and corporations with volume licensing and Software Assurance agreements for the Windows Enterprise edition will assign significant numbers of systems to the Long-term Servicing Branch (LTSB), a static channel that will resemble the historical practice of letting the code be, updating only for vulnerability patches and critical repairs. A LTSB build can be run, Microsoft has said, for as long as 10 years, but interim builds will be issued to refresh that branch every two or three years.

The upshot is that there will be a lot of different flavors of Windows 10 out and about concurrently.

"We've at least got five rings ... the 'ring count,' if you will," said Wes Miller of Directions on Microsoft, ticking off the Insider fast, Insider slow, CB, CBB and LTSB. "So that's at least five milestones to track. Then you've got different states of each: Customer has applied the latest patches or hasn't applied the latest patches. So that's at least 10."